As the areal density in newer disc drive designs increases, the magnetic spacing and fly height between the pole tips of the read/write heads and the magnetic storage media becomes correspondingly smaller. With these extremely small fly heights, manufacturing variations in the disc topography, particularly during seeking operations, can result in undesired transient mechanical contact between the head and the disc.
To reduce instances of undesired contact, there is a desire to use electrostatic type actuators in fly height control arrangements because of their low cost, low mass and low power consumption. Electrostatic actuators, however, generate an attractive force between the head and the disc that has an approximately inverse square relationship to the spacing. As the head moves closer to the disc, the attractive force increases exponentially. The electrostatic force can force the head to crash into the disc, resulting in damage to the head, the disc, or both. When the head is very close to the disc and the electrostatic actuator is used, the control of the fly height becomes unstable.
A method and an apparatus are needed to reduce the damage to heads or discs when a disc drive includes an electrostatic actuator controlling fly height spacing and the head contacts the disc.